Polysulfide as a novel chemical agent to solidify/stabilize lead in fly ash from municipal solid waste incineration

摘要

Polysulfide was produced and tested for use as an inexpensive chemical agent for the solidification/stabilization of lead in fly ash, generating little hydrogen sulfide gas. According to the equations S_n~(2-) → S + S_(n-1)~(2-) and S_n~(2-) + H~+ → HS~- + S_(n-1), this agent was expected to achieve long-term stability of disposed Pb. The leachate concentration of Pb in fly ash after sulfide treatment showed a decrease-increase-decrease trend. We also compared Pb leaching behavior from an aging/weathering experiment to ther-modynamic modeling using the database from the Geochemist's Workbench software. Thermodynamic modeling indicated the tendency that when the precipitate was formed in the order of PbO, PbCO_3·PbO, and PbCO_3, the total concentration of soluble Pb will be lowered. The leaching curve of Pb in fly ash without a lime slurry injection system was close to PbO, whose activity was initially near 1, but when leaching time increased, it shifted to that of PbCO_3·PbO, before finally ending at that of PbCO_3. However, Ca(OH)_2 sprayed on fly ash interfered with the carbonation process of Pb.